Personal communication system architecture

ABSTRACT

A personal communication system provides full duplex digital communications between multiple users for both audio and data. A universal adaptor interface receives a plurality of wireless communications. The wireless adaptor interface multiplexes the plurality of wireless communications into a composite signal. The universal adapter interface transmits the composite signal wirelessly. At least one personal communications unit receives the composite signal. Multiplexing the plurality of wireless communications facilitates simultaneous reception thereof by the personal communications units.

FIELD OF THE INVENTION

The present invention relates generally to communication systems andmore particularly to an architecture for a personal communication systemwhich provides full duplex digital voice and data communications betweenmultiple users via both wireless and wired systems.

BACKGROUND OF THE INVENTION

Wireless communications are well known. Such systems as walkie talkies,CB radios, and cellular telephones utilize wireless communications tofacilitate point-to-point communications between individuals atdifferent locations.

Such wireless communications systems typically utilize well known halfduplex or talk-then-listen radio methodology wherein a user can listento an incoming communication, or can speak, but not both simultaneously.Such half duplex wireless communication systems use either a push buttoncontrol or the like or alternatively use a voice operated switch (VOX)to change the mode of the transceiver from receive to transmit.

While such contemporary wireless communication systems have generallybeen suitable for their intended purposes, they possess the inherentdeficiency of requiring explicit actuation of the transmit mode via sucha manually operated or automatic switch and also suffer from theinherent deficiency of not permitting an incoming communication when thetransceiver is in the transmit mode.

Of course, requiring an operator to manually actuate the transmit mode,typically via a push button switch, necessitates that the operator use ahand (or possibly a foot) to key the microphone. Such explicit operationof the transceiver is not only a distraction, but may also be extremelyundesirable in instances where the operator's hands (and possibly feet)are otherwise occupied. For example, tank drivers, aircraft pilots,helicopter pilots, etc., particularly when engaged in demandingmaneuvers, may not be able to perform such manipulations, or may do soonly at the risk of neglecting some other task which requires immediateattention.

Voice operated switches have been developed in an attempt to mitigatethe problems associated with manually operated half duplex transceivers.However, such voice operated switches introduce an altogether new set ofproblems. Such problems include the operation of a voice operated switchin a high noise environment and the necessity of properly adjusting thesensitivity of the voice operated switch in such a high noiseenvironment. As those skilled in the art will appreciate, high levels ofambient noise frequently result in the undesirable and inadvertentkeying or actuation of the voice operated switch, such that no actualvoice transmission is broadcast and the transceiver is prevented fromaccepting incoming transmissions.

Also, the user of such a voice operated switch in a high noiseenvironment must speak louder than normal, so as to actuate even aproperly adjusted voice operated switch. Such loud speaking can befatiguing and may even result in hoarseness or other voice-relatedproblems.

Regardless of what type of half duplex transceiver is utilized (manuallyactuated or VOX), another problem associated with such half duplexsystems is the inadvertent keying thereof. Manually operated switcheshave an undesirable tendency to stick in the actuated position, therebyresulting in constant transmission and the inability to receivebroadcasts from other transceivers. Thus, the operator who has such astuck key can not even be notified by other individuals, who arelistening to the inadvertent broadcast, that his key is stuck in theactuator position, since the individual who has the stuck key isincapable of receiving broadcasts due to half duplex operation of thetransceiver. Further, as discussed above, voice operated switches maybecome inadvertently actuated due to high ambient noise levels.

As such, it is clear that a full duplex transceiver for point-to-pointcommunications would be desirable.

Wire intercoms are also well known. Frequently, such intercoms areconfigured such that a plurality of users may talk simultaneously withrespect to one another and each user may talk while listening to theconversations of a plurality of users. Thus, conversations via suchwired intercoms tend to be much more natural than those taking place viawireless, half-duplex wireless communication systems.

It would further be desirable to provide intercom-like operation of theradio transceivers, such that they are capable of receiving a pluralityof separate transmissions simultaneously, while the user is speaking. Inthis manner, each transceiver will pick up the broadcast of all othertransceivers so as to provide a much more natural means forcommunication.

It would further be desirable to provide a comprehensive communicationssystem which integrates wireless communications with wired intercomcommunications, such that persons utilizing a wired communicationssystem, such as that of a tank, aircraft, helicopter, etc., may readilycommunicate among one another, and may also, simultaneously if desired,communicate with persons who are not part of the wired intercom system.

SUMMARY OF THE INVENTION

The present invention specifically addresses and alleviates theabove-mentioned deficiencies associated with the prior art. Moreparticularly, the present invention comprises a method for providingfull duplex digital communications between multiple users, the methodcomprising the steps of: a universal adaptor interface (UAI) receiving aplurality of wireless communications; the universal adaptor interfacecombining or multiplexing the plurality of wireless communications intoa composite signal; the universal adaptor interface transmitting thecomposite signal; and at least one personal communications (PCU) unitreceiving the composite signal. The universal adapter interface (UAI)comprises a radio repeater and the personal communications unit (PCU)comprises a radio transceiver.

Multiplexing the plurality of wireless communication facilitatessimultaneous reception thereof by the personal communications unit. Thestep of multiplexing the plurality of wireless communications into acomposite signal preferably comprising summing the wirelesscommunications together. However, those skilled in the art willappreciate that various other methods of multiplexing the wirelesscommunications together to form a composite signal are likewisesuitable. For example, the wireless communications may be time splicedor otherwise multiplexed into a signal data stream. Preferably, thewireless communications are summed over a predetermined interval so asto define a frame.

The step of receiving a plurality of wireless communications maycomprise either receiving a plurality of audio signals, a plurality ofdata signals, or a combination of both audio and data signals. Thus, thecomposite signal may comprise either audio signals, data signals, or acombination of audio and data signals.

Optionally, the universal adaptor interface also receives one wiredintercom signal, which again may comprise either voice or data. Thewired intercom signal is combined with the plurality of wirelesscommunications to form the composite signal.

The personal communication units are configured so as to cooperate withthe universal adaptor interface when a universal adaptor interface isavailable, as to provide centralized control of a network defined by thepersonal communications unit and the interface adaptor.

In the group mode one UAI can co-operate with another UAI repeater, justas it can cooperate with a PCU.

The universal adaptor interface optionally transmits a composite signalto the wired intercom. In this manner, the universal adaptor interfaceprovides an optional bridge between wired and wireless communications ina manner which allows all of the users of both the wired and wirelesscommunications to speak simultaneously and also to hear all of theconversations via the composite signal received thereby.

The personal communication units are also preferably configured so as tocooperate with one another when a universal adaptor interface isunavailable, so as to provide distributed control of a network definedby the personal communications unit.

These, as well as other advantage of the present invention will be moreapparent from the following description and drawings. It is understoodthat changes in the specific structure shown and described may be madewithin the scope of the claims without departing from the spirit andscope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the personal communicationssystem of the present invention;

FIG. 2 is a block diagram of an exemplary network configurationaccording to the present invention;

FIG. 3 is a block diagram of a personal communications unit according tothe present invention;

FIG. 4 is a flow chart showing the operational states of a personalcommunications unit of the present invention;

FIG. 5 is a flow chart showing the stand-by mode of a personalcommunications unit of the present invention;

FIG. 6 is a flow chart showing the slave mode of a personalcommunications unit of the present invention;

FIG. 7 is a flow chart showing the autonomous mode (neighboring network)for a personal communications unit of the present invention;

FIG. 8 is a flow chart showing the autonomous mode (autonomous network)of a personal communications unit of the present invention;

FIG. 9 shows a protocol frame format of the present invention;

FIG. 10 shows a protocol slot format of the present invention;

FIG. 11 shows the protocol header format of the present invention;

FIG. 12 shows a message format for a downlink voice transmissionaccording to the present invention;

FIG. 13 shows a message format for an uplink voice transmissionaccording to the present invention (inhibit Sense Multiple Access);

FIG. 14 shows the interpretation of ISMA bits according to the presentinvention;

FIG. 15 shows protocol slot usage for autonomous mode operation with aneighboring network, according to the present invention; and

FIG. 16 is a graph showing communciations between a UAI and a PCU whenthe PCU is out of range with respect to the UAI.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiment of the invention, and is not intended to represent the onlyform in which the present invention may be constructed or utilized. Thedescription sets forth the functions and the sequence of steps forconstructing and operating the invention in connection with theillustrated embodiment. It is to be understood, however, that the sameor equivalent functions may be accomplished by different embodimentsthat are also intended to be encompassed within the spirit and scope ofthe invention.

Referring now to FIG. 1, when at least one universal adapter interface(UAI) 12 a is available, then all messages transmitted and received byeach personal communications unit (PCU) 10 a, 10 b, 10 c, are routedthrough the UAI 12 a which acts as a wireless network master. If morethan one UAI 12 a, 12 b is available, then one of the UAI's 12 a, 12 bis designated as the master UAI 12 a and the other is designated as thegroup UAI. In this mode, each PCU 10 a, 10 b, 10 c transmits its audiosignal to the master UAI 12 a. The master UAI 12 a then forms acomposite audio intercom signal by summing together all of the variousuplink PCU 10 a, 10 b, 10 c transmissions received during a given timeinterval or frame. If any UAI 12 a, 12 b is connected to a wiredintercom network 13 a, 13 b, then conversations from the wired intercom12 a, 13 b are included in the overall composite audio signal as well.

The master UAI 12 a transmits this composite audio signal to all of thePCU's 10 a, 10 b, 10 c within range, either as a general broadcastsignal or as a signal dedicated to a specific PCU 10 a, 10 b, 10 c, orboth. In addition, the master UAI 12 a may optionally transmit thewireless communications signals over the wired network, therebyproviding a bridge between wireless PCU's 10 a, 10 b, 10 c and wiredintercom 10 a, 10 b.

Autonomous mode is a more complex mode of PCU 10 a, 10 b, 10 c operationin which PCU's 10 a, 10 b, 10 c initiate communications in the absenceof a UAI 12 a, 12 b. A PCU 10 a, 10 b, 10 c that is out-of-range of aUAI 12 a, 12 b is referred to herein as an autonomous PCU 10 a, 10 b, 10c. Note that autonomous PCU's may initiate communications with otherPCU's 10 a, 10 b, 10 c already in a neighboring repeater-based network(one in which at least one UAI 12 a, 12 b is available), or with otherautonomous PCU's 10 a, 10 b, 10 c.

Referring now to FIG. 2 a repeater-based network containing one UAI 12and four PCU's 10 d-10 h is shown. PCU 10 h is within range of PCU 10 dand PCU 10 e, but out-of-range of the UAI 12. To ensure useful, reliableinformation exchange: 1) PCU 10 h preferably does not disrupt theexisting repeater-based network, and 2) PCU 10 h preferably is able tocommunicate with PCU 10 d and PCU 10 e.

These objectives are achieved through use of control fields contained inthe messages transmitted by each PCU 10 d-10 h. Specifically, anautonomous PCU (such as PCU 10 h) will search for uplink PCU 10 d-10 gtransmissions which indicate that a PCU 10 d-10 g within listening range(PCU 10 d or PCU 10 e) is part of a repeater-based network (a networkhaving at least one available UAI 12). Then, the autonomous PCU 10 hwill use the network status fields in these transmissions to determinethe network availability and system timing in the neighboring network.

The autonomous PCU 10 h will begin transmitting during time periods inwhich the neighboring network is inactive, and will include embeddedcontrol information that indicates that these messages correspond to anautonomous PCU 10 h. In this way, PCU's 10 d-10 g in the neighboringnetwork and within listening range of the autonomous PCU 10 h willdecode this control information and include the autonomous PCU's 10 hmessages in their composite audio signal.

In the event that an autonomous PCU 10 h does not detect the presence ofother PCU's 10 d-10 g, the autonomous PCU 10 h will begin broadcastingif it has radio data to transmit. Other autonomous PCU's 10 d-10 h inthe area will obtain network timing from this signal, and will establishcommunications using a procedure similar to the one describedpreviously.

PCU's 10 d-10 h are also capable of initiating point-to-point voicecommunications in which two PCU 10 d-10 h users converse privately. Forpoint-to-point operation, two PCU's 10 d-10 h use either auser-programmable identification (ID) number, or a read-onlymanufacturer ID number to provide network addressing. Also, in arepeater-based system (having at least one UAI 12), this conversationcan use the same wireless medium as the voice intercom withoutinterference.

Given that the communications system discussed herein employs a digitalwireless medium, applications requiring digital data communications aresupported as well. For example, some of the applications facilitated bythis system architecture include: remote database access (e.g., forimages, maps, etc.); remote report filing; reconnaissance (e.g.,transmission of images and sounds to a centralized facility); anduser-to-user data transfer.

Moreover, in a repeater-based network, digital data communications canoccur simultaneously with point-to-point voice intercom communicationsover the same wireless medium without interference. To achieve thissimultaneous operation, control information embedded in the PCU uplinkand UAI downlink transmissions are used to route intercom and datamessages to the appropriate PCU's.

A communications protocol for the present invention preferably utilizesa Time Division Multiple Access (TDMA) architecture in which each TDMAframe contains five (5) downlink and four (4) uplink slots, as discussedin detail below. Each slot is further divided into a synchronizationfield, a header field, a data field, and a CRC-16 field. In addition,Inhibit Sense Multiple Access (ISMA) is used as the Medium AccessControl (MAC) algorithm for determining slot availability.

Referring now to FIG. 3, the device architecture for each PCU 10 a-10 his shown. The major components of a PCU 10 a-10 h include: an audiocodec 30, a data port (e.g., an RS-232 interface) 32, a radio 40, anFPGA 36, and a DSP 38. The audio codec 30 provides an interface to anexternal headphone 24 and microphone (not shown), and/or an internalspeaker (not shown) and microphone (not shown). The radio 40 functionsas the interface to other PCUs and/or UAIs. The data port 32 is used tointerface the PCU 10 a-10 h with an external data terminal, for example,a personal computer 28. The user interface allows external control ofthe various PCU 10 a-10 h functions, for example, channel selection andvolume control. The FPGA 36 acts as a data interface between all ofthese components and the DSP 38. Finally, the DSP 38 implements thecontrol and signal processing algorithms used by the PCU 10 a-10 h.

The data flow and signal processing algorithms are as follows. The PCU10 a-10 h processes two separate, asynchronous data streams: the audioinput/output and the radio input/output. The timing for the radioinput/output data stream is determined by the TDMA framing. Receivedradio data is buffered in the FPGA 36 and read by the DSP 38 once acomplete TDMA slot is received. The DSP 38 decodes the header field anddetermines if the data field should be processed or ignored. Ifprocessing is required, the DSP 38 stores the data field in a circularbuffer corresponding to the current TDMA slot. Conversely, radio data tobe transmitted is written by the DSP 38 to a buffer in the FPGA 36. TheDSP then writes control information to the radio 40, causing the radio40 to transmit this data during the correct TDMA slot.

The sampling rate of the audio codec 30 determines the timing of theaudio input/output data stream, and ultimately the timing of the PCU 10a-10 h. Specifically, the audio codec 30 writes audio data received bythe microphone to the DSP 38. The DSP 38 processes this data using aVoice Activated Switch (VOX) algorithm, or a push-to-talk (PTT) switch,to determine if speech is present. At the start of an audio frame thePCU 10 a-10 h determines which received radio data slot buffers containvalid data. Any valid radio data is summed with the input audio signal,to form a composite audio output. The audio output is written to thecodec for transmission to the headphones 24 or speaker. Finally, if theVOX algorithm indicates that speech is present, or the PTT switch isactuated, the DSP 38 will use the audio input signal as the radio datato be transmitted during the next appropriate TDMA slot.

Besides data flow and signal processing, the DSP 38 also implements thecontrol algorithms that cause the PCU 10 a-10 h to operate in andtransition between the various protocol states, as well as the radiocontrol processing (e.g., frequency hopping, transmit and receive timingoutput power control, etc.).

Referring now to FIG. 4, each PCU 10 a-10 h can be in one of fourpossible protocol states or modes: Standby mode 50, Slave mode 56,Autonomous mode—Neighboring network 54, and Autonomous mode—Autonomousnetwork 52.

A PCU 10 a-10 h is in Slave mode 56 if it is linked to a master UAI 12 a(FIG. 1). A PCU 10 a-10 h is in Autonomous mode—Neighboring network 54if it is linked to PCU's 10 a-10 h that are members of a repeater-basednetwork. A PCU is in Autonomous mode—Automous network if it is linked toPCUs that are not members of a repeater-based network. A PCU 10 a-10 his in Standby mode 50 if it is attempting to determine the currentnetwork configuration. Referring now to FIGS. 5-8, the possiblestate/mode transitions, and the control processing that occurs withineach possible state/mode are shown.

According to the preferred embodiment of the present invention thelength of an audio frame equals the length of a TDMA frame. Since theaudio and TDMA frames are typically offset with respect to one another,block data processing is used in which the start of the audio frameindicates the start of the block of data to be processed.

An example of a system architecture for versatile, wireless voice anddata communications is depicted in FIG. 1. In general, this systemcontains two main components: repeaters, or Wireless Interface Adapters(UAIs) 12 a, 12 b, and Personal Communications Units (PCUs) 10 a, 10 b,10 c. In its standard mode of operation, a UAI 12 a, 12 b is a devicethat provides centralized control of the wireless network by receiving,processing and routing incoming PCU 10 a, 10 b, 10 c transmissions. APCU 10 a, 10 b, 10 c is a device that provides an individual user withaccess to the wireless network. In its standard mode of operation, thePCU 10 a, 10 b, 10 c requests network access from the corresponding UAI12 a, 12 b, and begins transmitting once access is granted. In thismode, messages transmitted and received by the PCU 10 a, 10 b, 10 c arerouted through the UAI 12 a, 12 b. However, the PCU's 10 a, 10 b, 10 care also capable of forming a network in the absence of a UAI 12 a, 12b. In this case, the PCUs use distributed control to establish thenetwork and grant network access. Note that the switch betweencentralized and distributed controls occurs automatically and seamlesslyas the network topology changes.

UAIs 12 a, 12 b in a wireless intercom network may also be connected towired intercom. As such, the UAI 12 a, 12 b acts as a bridge betweenusers of the wireless intercom and users of the wired intercom. The UAI12 a, 12 b sends the composite wired and wireless intercom voice signalto the wireless users during its downlink transmissions. Conversely, theUAI 12 a, 12 b combines all uplink wireless messages to form a compositesignal that is transmitted to all wired intercom users. A more detaileddiscussion regarding the intercom communications is provided in the nextsection.

System operation for the case of wireless voice intercom communicationsis discussed below. In this case, the system components (UAI 12 a, 12 band PCUs 10 a, 10 b, 10 c) may operate in one of three modes: repeatermode, autonomous mode and group mode.

Repeater mode is the standard mode of network operation in which the UAI12 a, 12 b is the wireless network master. In this mode the UAI 12 a, 12b receives multiple uplink transmissions from a number of PCUs 10 a, 10b, 10 c. The UAI 12 a, 12 b then forms a composite audio intercom signalby summing together all of the uplink PCU transmissions received duringa given time interval, or frame. If the UAI 12 a, 12 b is also connectedto a wire intercom network, it can include those conversations in theoverall composite audio signal as well. Finally, the UAI 12 a, 12 btransmits this composite audio signal to all PCUs 10 a, 10 b, 10 c inrange. In addition, the UAI 12 a, 12 b may transmit the wirelessintercom signals over the wired network, thereby providing a bridgebetween wired and wireless intercom users.

Autonomous mode is the more complex mode of network operation in whichPCUs 10 a, 10 b, 10 c initiate communications in the absence of a UAI 12a, 12 b. A PCU 10 a, 10 b, 10 c that is out-of-range of a UAI is calledan autonomous PCUs 10 a, 10 b, 10 c. Note that autonomous PCUs 10 a, 10b, 10 c may initiate communications with other PCUs 10 a, 10 b, 10 calready in a neighboring, repeater-based network, or with otherautonomous PCUs 10 a, 10 b, 10 c.

Given that the system architecture discussed herein employs a digitalwireless medium, applications requiring digital data communications aresupported as well. For example, some of he applications facilitated bythis system architecture include:

Remote database access (e.g., for images, maps, etc.);

Remote report filing;

Reconnaissance (e.g., transmission of images and sounds to a centralizedfacility); and

User-to-user data transfer.

Moreover, in a repeater-based network, digital data communications canoccur simultaneously with point-to-point voice intercom communicationsover the same wireless medium without interference. To achieve thissimultaneous operations, the UAI uses control information embedded inthe uplink and downlink transmissions to route intercom and datamessages to the appropriate PCUs.

The system architecture preferably has the characteristics listed below:

TABLE 1 System Characteristics Parameter Value Comment Range 1500 ft.typical Channel type Time division duplex, frequency simplex Data rate 1Mbps Physical layer Frequency hopping FCC complaint in spread spectrumthe 2.45 GHz ISM band No. of hopping 75 Per FCC 15.247 Operating2400-2483.5 Per FCC 15.247 frequency range MHz Number of 64 Each channelis distinct assigned a channels distinct hopping pattern Physical layerTime division 4 uplink slots; 1 frame format multiple access repeaterdownlink (TDMA) slot; 4 dedicated downlink slots Number of 4 PCUsunlimited number simultaneous transmitting, and of listeners intercomtalkers a wired intercom if connected to the UAI; Medium access Inhibitsense control (MAC) multiple access layer (ISMA) Networking modesRepeater-based, autonomous, and group Echo suppression UAI controlledFacilitated by the dedicated downlink slots and an echo suppressionalgorithm Sidetone Locally generated Audio format 8 bit μ-law PCM

The method for implementing a time division multiple access protocol fordigital communications according to the present invention is illustratedin FIGS. 2 and 9-15, which depict a presently preferred embodimentthereof.

The protocol described herein was developed for use in a wirelesscommunications system containing multiple Personal Communication Units(PCUs) and multiple repeaters. A PCU is a device that provides a userwith access to the wireless network. A repeater is a device thatcontrols the wireless network traffic and may be connected to anadditional wired network. To achieve the system features discussedpreviously, the protocol utilizes a Time Division Multiple Access (TDMA)architecture that provides multiple users with simultaneous access tothe transmission medium.

Referring now to FIG. 9, the protocol is divided into frames that aretransmitted sequentially in time. Each frame contains a number of TDMAslots D0-U4. Slots D1 through D4 and U1 through U4 are downlink(transmission from repeater to PCU) and uplink (transmission from PCU torepeater) slots, respectively. Usually, downlink and uplink slots havingthe same index (e.g., D1 and U1) are linked to form a downlink-uplinkslot pair. In a typical system, multiple PCUs will use a Medium AccessControl (MAC) algorithm to access the available uplink slots. Once a PCUobtains access to an uplink slot, it receives transmissions from therepeater during the corresponding downlink slot. Those PCUs that do nothave access to an uplink slot will receive broadcast repeatertransmissions during the downlink slot D0. Finally, a frame gap isprovided so that frames do not overlap due to clock inaccuracies, andfor synthesizer re-programming in a Frequency Hopping (FH) SpreadSpectrum (SS) system.

Referring now to FIG. 10, each slot in the protocol frame is segmentedinto a number of fields. Each slot contains a preamble and slot syncfield for radio acquisition, a header field for control information, adata field for audio and digital information, a 16-bit CRC field forerror detection, and a slot gap to allow for clock inaccuracies.

Referring now to FIG. 11 the header format for all slots is depicted.The generic format of the header permits protocol “layering” and thereserved field permits future protocol growth. Also, theuser-programmable ID field permits the point-to-point communicationspreviously discussed.

The eight (8) bit Message type field permits 256 possible types ofmessages. Those currently defined are listed in Table 1 and discussed inthe following sections.

TABLE 1 Defined Message Types MESSAGE TYPE DESCRIPTION 80 h Downlinkvoice message 01 h Uplink voice message for PCUs in a repeater-basednetwork, or in range of PCUs in a repeater-based network 08 h Uplinkvoice message for autonomous PCUs out of range of a repeater 00 h, 02h-07 h, 09 h-7 fh, To be defined (for point- 81 h-FFh to-pointconversations, data communications, testing, etc.

This section describes the message types used to provide voice intercomcommunications. In the standard repeater mode of network operation, therepeater receives multiple uplink transmissions from a number of PCUs.The repeater then forms a composite audio intercom signal by summingtogether all of the uplink PCU transmissions received during a givenprotocol frame. If the repeater is also connected to a wired intercomnetwork, it can include those conversations in the overall compositeaudio signal as well. Finally, the repeater transmits this compositesignal to all PCUs in range using the appropriate downlink slots. Inaddition, the repeater may transmit the wireless intercom signals overthe wired network, thereby providing a bridge between wired and wirelessintercom users.

Referring now to FIG. 12, voice intercom transmissions sent by arepeater during a downlink slot use Message Type 80h. For Message Type80h, the Message Subtype, ID, and Reserved fields for standard voiceintercom communications are unused and are set to 00h. The “Master” and“Autonomous” bits are interpreted according to Table 2. For downlinktransmission, the repeater will send (Master, Autonomous)=(1,0).

TABLE 2 Interpretation of Master and Autonomous Bits Bit BitInterpretation 0 0 A PCU in slave mode, or a repeater in Group mode andslaved to a master repeater. 0 1 A PCU or a repeater (Group mode) inautomous-slave mode. 1 0 A repeater in master mode 1 1 A PCU or arepeater (Group mode) in autonomous- master mode.

The six (6) channel bits are used to represent up to 64 distinctwireless channels. The Inhibit Sense Multiple Access (ISMA) bits areinterpreted according to FIG. 14, and are used to facilitate MACprocessing. The “reserved” bit is currently unused and set to 0.Finally, the “Active Slot” bit field is used to represent the currentactive slot, and is interpreted according to Table 3.

TABLE 3 Interpretation of Active Slot Bit Field Active Slot FieldInterpretation 100 Repeater transmitting in Slot D0 100 Repeatertransmitting in Slot D1 001 Repeater transmitting in Slot D2 010Repeater transmitting in Slot D3 011 Repeater transmitting in Slot D4

Referring now to FIG. 13, voice intercom transmissions sent by PCU (orrepeater in Group mode) during an uplink slot use Message Type 01h, asshown in FIG. 13. As for Message Type 80h, the Message Subtype, ID, andReserved fields for standard voice intercom communications are currentlyunused in Message Type 01h, the “Master” and “Autonomous” bits areinterpreted according to Table 2, and the six (6) channel bits are usedto represent up to 64 distinct wireless channels.

Referring now to FIG. 14, the ISMA bit field is interpreted as shown, if(Master bit, Autonomous bit)=(0, 0), otherwise the ISMA bits areignored. The “PTT” equals “1” if the push-to-talk switch on the PCU isdepressed, otherwise it is set to “0”. The “Reserved” bit is currentlyunused and set to “0”. Finally, the “Active Slot” bit field is used torepresent the current slot, and is interpreted according to Table 4.

TABLE 4 Interpretation of Active Slot Bit Field Active Slot FieldInterpretation 00 PCU transmitting in Slot U1 01 PCU transmitting inSlot U2 10 PCU transmitting in Slot U3 11 PCU transmitting in Slot U4

In Inhibit Sense Multiple Access (ISMA), the network master (repeater)transmits information regarding slot availability. PCUs use thisinformation to randomly access one of the available uplink TDMA slots.Specifically, the ISMA technique used in this protocol is as follows:

1. The repeater transmits a busy/free flag for each TDMA slot in aframe;

2. PCUs in the network echo the ISMA information in their uplink headerfield.

3. PCUs do not attempt to access a slot that is busy;

4. PCUs will randomly attempt to access slots that are free;

5. After accessing a slot, a PCU monitors the busy/free flag for thatslot during the next few frames. If the flag is not set to busy after apredetermined number of frames, the PCU stops transmitting since itstransmission was not received by the repeater, most likely due to acollision with another PCU transmission.

Repeater mode is the standard mode of network operation in which therepeater is the wireless network master. In this mode, the repeaterdetermines the network timing (e.g., frame start and end) andfacilitates downlink-uplink slot pairing.

Autonomous mode is the more complex mode of network operation in whichPCUs initiate communications in the absence of a repeater. A PCU that isout-of-range of a repeater is called an “autonomous PCU”. Note thatautonomous PCUs may initiate communications with other PCUs already in aneighboring, repeater-based network, or with other autonomous PCUs.

Referring again to FIG. 2, a repeater-based network containing arepeater 12 and four (4) PCUs 10 d-10 h is shown. PCU 10 h is withinrange of PCU 10 d and PCU 10 e, but out-of-range of the repeater 12. Asdiscussed above, to ensure useful, reliable information exchange: 1) PCU10 h should not disrupt the existing repeater-based network, and 2) PCU10 h should be able to communicate with PCU 10 d and PCU 10 e. Thesegoals are achieved through use of the ISMA, Master, and Autonomous bits,and the Active Slot field in message type 01h. Specifically, anautonomous PCU (PCU 10 h) will look for uplink slot transmissions with(Master, Autonomous)=(0, 0), which indicates that the PCU (PCU 10 d orPCU 10 e) within listening range is part of a repeater-based network.Then, the autonomous PCU 10 h will decode the ISMA bits echoed in thereceived message header to determine the slot availability in theneighboring network. Finally, the autonomous PCU 10 h will use theActive Slot field to determine the system timing of the neighboringnetwork, and will begin transmitting during one of the available slots,using Message Type 01h with (Master, Autonomous)=(0, 1). PCU 10 d-10 g,in the neighboring network and within listening range of the autonomousPCU 10 h will decode this Master-Autonomous PCU's message in theircomposite intercom audio signal.

Referring now to FIG. 15, the protocol slot contents and resultingintercom audio signals for this example are depicted for therepeater-based network shown in FIG. 2 with PCUs 10 d-10 g in range ofthe repeater and autonomous PCU 10 h in range of PCUs 10 d and 10 e.

In the event that an autonomous PCU does not detect the presence ofother PCUs, the autonomous PCU will start broadcasting Message Type 08hwith (Master, Autonomous)=(1, 1), and with the ISMA bits and Active Slotfield set to indicate that slot U1 is active. Other autonomous PCUs inthe area will obtain network timing from this signal, and will establishcommunications using Message Type 08h with (Master, Autonomous)=(0,1)and a procedure similar to the one described previously.

Repeaters in the wireless intercom network may also be connected to awired intercom. As such, the repeater acts as a bridge between users ofthe wireless intercom and users of the wired intercom. The repeatersends the composite wired intercom voice signal to the wireless usersduring its downlink slot transmission. Conversely, the repeater combinesall wireless transmission received in the uplink slots to form acomposite signal that is transmitted to all wired intercom users.

The Group mode of operation can be used to connect two or more wiredintercom networks together, along with other wireless intercom users.Specifically, a repeater in Group mode is configured to function as aPCU having the wired intercom as its audio input signal. Since therepeater acts as a PCU, it can communicate with other repeaters and PCUsusing the repeater and autonomous modes discussed previously.

Point-to-point voice communications in which two users converseprivately are also possible within the framework of this protocol. Forthis mode of operation, two PCUs would use either the user-programmableID header field, or a read-only manufacturer ID number to directmessages between each other and not over the intercom network. Also, ina repeater-based system, this conversation can use the same wirelessmedium as the voice intercom without interference. Note that additionalmessage types (i.e., a subset of the types 00h, 02h-07h, 09h-7Fh,81h-FFh in Table 1) will be defined to support point-to-pointcommunications.

In the repeater-based network of the present invention, digital datacommunications can occur simultaneously with point-to-point voiceintercom communications over the same wireless medium withoutinterference. Note that additional message types (i.e., a subset of thetypes 00h, 02h-07h, 09h-7Fh, 81h-FFh in Table 1) will be defined tosupport data communications.

Flow charts showing the operation of the present invention are providedin FIGS. 5-8, which are discussed in detail below.

With particular reference to FIG. 5, a flow chart of the PCU standbymode is provided. The PCU standby mode 60 may be entered from PCU powerup, new channel selection, PCU autonomous mode-neighboring network, orPCU autonomous mode-autonomous network.

The PCU receiver monitors 62 the default channel frequency for up to 80frame intervals or frequency hops. If no preamble is detected 64, then acheck is made to see if more than 80 frame intervals have passed. Ifnot, then the PCU continues to monitor 62 the default channel. Ifgreater than 80 frame intervals have passed, the PCU commencesautonomous mode—autonomous network operation 68.

When a preamble is detected 64, then the channel number and slot number70 are determined. If the channel is not correct 72, then the PCUmonitors 62 the default channel again. If the channel is correct 72,then the message type is decoded. If a downlink slot message type 80h isreceived, then the PCU enters 80 to slave mode. If an uplink slotmessage type 01h is received, the PCU enters 82 the autonomousmode-neighboring network. Otherwise, if an uplink slot message type 08his received, then the PCU enters the autonomous mode-autonomous network84.

With particular reference to FIG. 6, a flow chart of the PCU slave modeis provided. The PCU slave mode 100 is entered from the PCU standbymode, the PCU autonomous mode-neighboring network or the PCU autonomousnetwork. After entering the PCU slave mode 100, the system decodes theheader for slot D0, if present, and stores UAI data 102. If a UAI is notdetected 104, then PCU autonomous mode-neighboring network 106 isentered. If a UAI is detected 104, then check is made to see if there isradio data to transmit 108. If not, then the header is decoded for alluplink slots and data stored for autonomous PCU's 114. Also, audio datain the buffers for slot D0 and uplink slots containing autonomous PCUdata are summed 120 and audio data is sent 126 to the headset. Thesystem then waits for the end of frame and hops 132 to the nextfrequency, then resumes decoding headers for slot, D0 if resent, andstoring UAI data 102. When radio data to transmit is present 108, or ifa beacon interval for autonomous PCU timing has been exceeded, then acheck is made to see if the system is currently transmitting 110. If thesystem is not currently transmitting 110, then the ISMA flags receivedin the UAI transmissions are used to determine uplink slot status 116and a check is made to see if a slot is available 122. If no slot isavailable 122, then the system decodes the header for all uplink slotsand stores data for autonomous PCU's 114. If a slot is available 122,then a transmission is made on a randomly selected available uplink slot128.

If the system is currently transmitting 110, then slot access isverified 112. If valid slot access for the current slot is yet to beverified, then the setting of the ISMA flag for the current slot ischecked 124. If the flag is not set 124, then a check is made foranother available slot 122.

If the flag for the selected slot busy is set 124 or if the slot accesshas already been verified 112, then the system continues to transmit onthe selected uplink slot 130. The system decodes the header for thededicated downlink and all uplink slots and stores available audio data134. Audio data in the buffers for the selected downlink slot and alluplink slots containing autonomous PCU data are summed 136 and the audiodata is sent to the headset 126.

With particular reference to FIG. 7, a flow chart for the PCU autonomousmode-neighboring network is provided. The PCU autonomousmode-neighboring network is entered from the PCU standby mode, the PCUslave mode, or the PCU autonomous mode-autonomous network. If present,the header for slot D0 is decoded and UAI data is stored 152. If a UAIis detected, then the PCU slave mode is entered 156. If a UAI is notdetected, then the headers for all uplink slots are decoded and data forautonomous PCUs is stored 158. If no uplink slot is detected 160, thenPCU standby mode is entered 162. If an uplink slot is detected 160, thena check is made to see of there is data to transmit 164. If there is nodata to transmit 164, then audio data in the buffers for uplink slotscontaining PCU data is summed 170 and the resulting audio data is sent176 to the headset. Then, the system waits for the end of the currentframe and hops 182 to a new frequency.

When there is data to transmit 164, or if a beacon interval forautonomous PCU timing has been exceeded, then a check is made to see ifthe system is currently transmitting 166. If the system is not currenttransmitting 166, then a determination is made to see if a slot isavailable via the ISMA control fields received in the uplink slots 172.If no slot is available 178, then the system sums audio data in buffersfor uplink slots containing PCU data 170. If a slot is available 178,then the system transmits 184 on a randomly selected available uplinkslot.

When a check that the system is currently transmitting is positive 166,then a determination is made to see if a slot collision has occurred168. This utilizes information in the headers of uplink PCUtransmissions to signal if autonomous PCU data is received. If slotaccess is not verified, then a check is made for another available slot178. If slot access is verified, then the PCU continues to transmit 180in the selected uplink slot.

With particular reference to FIG. 8, a flow chart for the PCU autonomousmode-autonomous network is provided. The PCU autonomous mode-autonomousnetwork 200 is entered only from the PCU standby mode. After enteringthe PCU autonomous mode-autonomous network 200, the system decodes theheader for slot D0, if present, and stores UAI data 202. If a UAI isdetected 204, then the PCU slave mode 206 is entered. If a UAI is notdetected, then the system decodes the header for all uplink slots andstores data for autonomous PCUs 214. If an uplink slot is not detected222, and no PCUs have been detected for a predetermined period of time,then the system enters the PCU standby mode 240.

If an uplink slot was detected 222, then a check is made to see if thereis a UAI in the area 216. If there is a UAI in the area 216, then thePCU enters the PCU autonomous mode-neighboring network 208. If no UAI isin the area, then the autonomous network timing is determined 224. Ifthere is no data to transmit, then audio data in the buffers for uplinkslots containing PCU data is summed 238 and audio data is sent to theheadset 242. Then the system waits for the end of the current frame andhops 244 to a new frequency.

If there is data to transmit 230, 232, then a check is made to see ifthe system is currently transmitting data 210. If not, then adetermination of slot availability is performed using the control fieldsreceived in the transmission of other autonomous PCUs 218, 226. If noslot is available, then the PCU sums audio data in the buffers foruplink slots containing PCU data 238. If a slot is available, then thesystem transmits on a randomly selected available uplink slot 234.

If the check to see if the system is currently transmitting 210 resultsin a positive indication, then a determination is made as to whether ornot there is a slot collision 212. This uses information in the headerof the received uplink PCU transmissions to signal if the previouslyautonomous PCU data was received.

A check is made to see if access for the selected slot has been verified220. If slot access is not verified 220, then a check is made foradditional available slots 226. If slot access is verified, then the PCUtransmits in the selected uplink slot 228.

Referring now to FIG. 16, the present invention preferably comprises amethod for relaying communications from a PCU which is out of transmitrange with respect to the UAI, but which is within receive rangethereof. That is, the PCU is so far away from the UAI that it cannottransmit messages thereto, but the PCU is close enough to the UAI thatit can receive messages therefrom. Those skilled in the art willappreciate that this is a common occurrence, since the UAI willtypically have a greater power output than the PCUs.

When a first PCU is incapable of transmitting to the UAI, a second PCUwhich is capable of receiving communications from the first PCU andwhich is also capable of transmitting to the UAI, relays communicationsfrom the first PCU to the UAI.

The second PCU may sense the need to perform such relaying ofcommunications from the first PCU to the UAI by monitoringcommunications between the first PCU and the UAI. During such monitoringof the communications between the first PCU and the UAI, the second PCUmay notice that the first PCU is not transmitting to the UAI during itsallocated time slot. Alternatively, the second PCU may notice the lackof a communication received acknowledgment in the UAIs transmission tothe first PCU. As a further alternative, the first PCU may add a flag orother message to it own header indicating its inability to communicatewith the UAI and thereby requesting that another PCU relaycommunications for it.

For example, at time T₁ the first PCU transmits to the UAI. Then, attime T₂ the UAI transmits back to the first PCU. However, if the UAIdoes not acknowledge receipt of the transmission from the PCU at timeT₁, then the first PCU may not transmit during its next allocated time,i.e., at time T₃. At time T₄ the UAI attempts to again establishcommunications with the first PCU.

When such inability of the first PCU to transmit successfully to the UAIis noticed by a second PCU, which is capable of communicating with theUAI, then the second PCU relays communications between the first PCU andthe UAI.

It is understood that the exemplary personal communication systemdescribed herein and shown in the drawings represents only a presentlypreferred embodiment of the invention. Indeed, various modifications andadditions may be made to such embodiment without departing from thespirit and scope of the invention. Further, various modifications andadditions may be obvious to those skilled the art and may be implementedto adapt the present invention for use in a variety of differentapplications.

What is claimed is:
 1. A method for providing full duplex digitalcommunications within a network defined by at least one transceiver, arepeater and at least one wired intercom system, the method comprisingthe steps of: a) receiving with the repeater at least one wirelesscommunication from the transceivers(s); b) receiving with the repeaterat least one wired intercom signal from the wired intercom system(s); c)multiplexing with the repeater the wireless communication(s) and thewired intercom signal(s) to form a composite signal; d) transmitting thecomposite signal wirelessly from the repeater to other transceiver(s);and e) receiving with the other transceiver(s) the composite signal; f)wherein multiplexing the wireless communication(s) and the wiredintercom signal(s) facilitates simultaneous reception thereof.
 2. Themethod as recited in claim 1, wherein the step of multiplexing thewireless communication(s) and the wired intercom signal(s) into acomposite signal comprises summing the wireless communication(s) and thewired intercom signal(s) together.
 3. The method as recited in claim 1,wherein the step of multiplexing the wireless communication(s) and thewired intercom signal(s) into the composite signal comprises summing thewireless communication(s) and the wired intercom signal(s) over apredetermined time interval.
 4. The method as recited in claim 1,wherein: a) the step of receiving the wireless communication(s)comprises receiving at least one transceiver audio signal; b) the stepof receiving the wired intercom signal(s) comprises receiving at leastone intercom audio signal; and c) the step of multiplexing the wirelesscommunication(s) and the wired intercom signal(s) into the compositesignal comprises multiplexing the wireless communication(s) and thewired intercom signal(s) into a composite audio signal.
 5. The method asrecited in claim 1, wherein: a) the step of receiving the wirelesscommunication(s) comprises receiving at least one transceiver audiosignal and at least one transceiver data signal; b) the step ofreceiving the wired intercom signal(s) comprises receiving at least oneintercom audio signal and at least one intercom data signal; and c) thestep of multiplexing the wireless communication(s) and the wiredintercom signal(s) into the composite signal comprises multiplexing thewireless communication(s) and the wired intercom signal(s) into acomposite audio/data signal.
 6. The method as recited in claim 1,further comprising the step of transmitting the composite signal to awired intercom.
 7. The method as recited in claim 1, further comprisingthe steps of: a) providing centralized control of a network defined bytransceivers and at least one repeater; and b) cooperating amongtransceivers when a repeater is unavailable, so as to providedistributed control of the network defined by the transceivers.
 8. Themethod as recited in claim 1, further comprising the step of performingpeer-to-peer communications.
 9. The method as recited in claim 1,further comprising the step of linking of multiple wired intercoms witha repeater.
 10. A communications system for providing full duplex audiocommunications within a network defined by at least one transceiver, arepeater and at least one wired intercom system, the communicationssystem comprising: a) a repeater for receiving a plurality oftransceiver audio signals and at least one wired intercom audio signal,the repeater having a multiplexer for multiplexing the plurality oftransceiver audio signals and the at least one wired intercom audiosignal into a composite audio signal, the repeater further having atransmitter for transmitting the composite audio signal wirelessly; b)at least one transceiver for receiving the composite audio signal; andc) wherein multiplexing the plurality of transceiver audio signals andthe at least one wired intercom audio signal facilitates simultaneousreception thereof by the at least one transceiver.
 11. Thecommunications system as recited in claim 10 wherein the multiplexercomprises a summer for summing the plurality of transceiver audiosignals and the at least one wired intercom audio signal together. 12.The communications system as recited in claim 11 wherein the summer isconfigured to sum the plurality of transceiver audio signals and the atleast one wired intercom audio signal over a predetermined timeinterval.
 13. The communications system as recited in claim 10, wherein:a) the repeater is configured to receive at least one transceiver audiosignal and at least one transceiver data signal; b) the repeater isconfigured to receive at least one wired intercom audio signal and atleast one wired intercom data signal; and c) the repeater is configuredto multiplex the at least one transceiver audio signal, the at least onetransceiver data signal, the at least one wired intercom audio signaland the at least one wired intercom data signal into a compositeaudio/data signal.
 14. The communications system as recited in claim 10,wherein the repeater is configured to transmit the composite audiosignal to a wired intercom.
 15. The communications system as recited inclaim 10, wherein: a) at least one transceiver is configured tocooperate with the repeater when the repeater is available, so as toprovide centralized control of the network defined by the transceiversand the repeater; b) the transceivers are configured to cooperate withone another when a repeater is unavailable, so as to provide distributedcontrol of a network defined by the transceivers; and c) an autonomoustransceiver of a neighboring network cooperates with other transceiversin that network so as not to bring down that network.
 16. Thecommunications system as recited in claim 10, wherein the transceiver(s)are configured so as to facilitate peer-to-peer communication among oneanother.
 17. The communications system as recited in claim 10, whereinthe repeater is configured so as to function as a transceiver so as tofacilitate linking of multiple wired intercom therewith.
 18. Acommunications system for facilitating full duplex communication betweena network defined by a plurality of radio transceivers and a wiredintercom system, the system comprising: a) a plurality of radiotransceivers transmitting transceiver signals therebetween and defininga transceiver network; b) at least one wired intercom systemtransmitting at least one wired intercom signal; and c) a repeaterinterfacing the network and the wired intercom system(s), the repeaterbeing operative to receive the transceiver and at least one wiredintercom signals to form a first composite signal therefrom forcommunication to the plurality of transceivers.
 19. The system as setforth in claim 18 wherein the repeater is further configured to form asecond composite signal comprised of the signals from the plurality oftransceivers for communication to the wired intercom system.
 20. Thesystem as set forth in claim 18 wherein the wired intercom system isinstalled within a vehicle.
 21. The system as set forth in claim 18wherein each transceiver comprises an antenna for radio frequencycommunication with other transceivers.
 22. The system as set forth inclaim 18 wherein the repeater further comprises a multiplexer forcombining the transceiver and at least one wired intercom signals. 23.The system as set forth in claim 18 wherein the repeater is configuredto receive audio and data signals from the transceivers, and to form thefirst composite signal therefrom.
 24. The system as set forth in claim18 wherein the repeater is configured for centralized control of thenetwork such that the repeater receives, transmits and regulatestransceiver signals between the transceivers.
 25. The system as setforth in claim 24 wherein the transceivers are configured fordistributed control of the network such that the transceivers areoperable to communicate directly with one another when the repeater isinoperative.
 26. The system as set forth in claim 18 wherein therepeater is in wired communication with the wired intercom system(s).27. The system as set forth in claim 18 wherein the repeater is inwireless communication with the wired intercom system(s).
 28. Acommunications system for providing full duplex communication within anetwork defined by a plurality of radio transceivers and a repeater, thesystem comprising: a) a plurality of radio transceivers in wirelesscommunication therebetween and defining a transceiver network; and b) arepeater for receiving a plurality of wireless communications from thetransceivers to form a composite signal therefrom, the repeater furtherbeing operative to transmit the composite signal to the plurality oftransceivers; c) wherein: 1) the transceivers are configured fordistributed control of the network such that the transceivers areoperable to communicate directly with one another when the repeater isinoperative; and 2) the repeater is configured for centralized controlof the network such that the repeater receives, transmits and regulatessignals between the transceivers.
 29. The system as set forth in claim28 wherein each transceiver comprises an antenna for radio frequencycommunication with other transceivers.
 30. The system as set forth inclaim 28 wherein the repeater is configured to receive voice and datasignals from the transceivers, and to form the composite signaltherefrom.
 31. The system as set forth in claim 28 wherein the pluralityof wireless communications comprise a plurality of separately timedsignal segments.
 32. The system as set forth in claim 31 wherein eachsegment comprises a plurality of downlink and uplink slots, each downlink slot including transmissions from the repeater to the transceiverstherein, and each uplink slot including transmissions from thetransceivers to the repeater therein.
 33. The system as set forth inclaim 28 wherein the repeater further comprises a multiplexer forcombining the plurality of wireless communications.
 34. The system asset forth in claim 33 wherein the multiplexer comprises a summer forsumming the plurality of wireless communications together.
 35. Thesystem as set forth in claim 34 wherein the summer is configured to sumthe plurality of wireless communications during a predetermined timeinterval.
 36. The system as set forth in claim 28, wherein: a) therepeater is configured to receive a plurality of audio signals; and b)the repeater is configured to multiplex the plurality of audio signalsinto a composite audio signal.
 37. The system as set forth in claim 28further comprising at least one wired intercom system, wherein: a) therepeater is configured to receive at least one wired intercom signal;and b) the repeater is further configured to multiplex the at least onewired intercom signal with the plurality of wireless communications toform the composite signal.
 38. The system as set forth in claim 28wherein the transceivers are configured so as to facilitatepoint-to-point communication among one another.
 39. The system as setforth in claim 28 wherein an autonomous transceiver of a neighboringnetwork communicates with other transceivers in the network so as not tobring down that network.
 40. The system as set forth in claim 28 furthercomprising at least one wired intercom system, and wherein the repeateris configured to transmit the composite signal to the at least one wiredintercom system.